Role of adjuvant radiotherapy in extrahepatic bile duct cancer: A multicenter retrospective study (Korean Radiation Oncology Group 18-14)

Purpose: To evaluate the role of adjuvant radiotherapy (RT) after curative resection in patients with extrahepatic bile duct (EHBD) cancer. Methods: Between January 2000 and December 2015, 1475 patients with EHBD cancer who underwent curative resection were accrued from 14 institutions in Korea. Among these, 959 patients did not receive any adjuvant therapy (RT(−) group), while 516 underwent postoperative RT with or without chemotherapy (RT(+) group). Results: The median age was 67 years. Nodal involvement was present in 482 patients (32.7%), and resection margin was involved in 293 patients (19.9%). RT(+) group had more patients with proximal tumours, advanced tumours, nodal involvement, perineural invasion, and involved resection margin than RT(−) group (all p < 0.001). With a median follow-up of 36 months, there were 211 locoregional recurrences, 307 distant metastases and 322 combined locoregional and distant failures. On multivariate analysis incorporating age, tumour location, differentiation, pT classification, pN classification, perineural invasion and resection margin, adjuvant RT was associated with improved overall survival (hazard ratio, 0.74; 95% confidence interval, 0.63–0.86; p < 0.001). When RT(+) group was separated into RT alone, concurrent chemoradiotherapy (CCRT) and CCRT followed by chemotherapy, the greatest benefit was observed in patients treated with CCRT followed by chemotherapy (hazard ratio, 0.52; 95% confidence interval, 0.41–0.68). Conclusions: Adjuvant RT combined with chemotherapy improved survival outcomes of resected EHBD cancer patients. Considering the greatest benefit observed in patients receiving CCRT followed by chemotherapy, a randomised controlled trial comparing chemotherapy alone and CCRT followed by chemotherapy is urgently needed.